Video images and images often contain smoothly changing areas such as blue-sky background and shadings on the wall. In such areas, image luminance is changing gradually, which should be perceived as smooth areas. However, as images are stored digitally as pixels and the bit depth is limited, stage-like false contour artifacts may be perceptible in these areas.
To eliminate such artifacts, a higher precision content of the smoothly changing image area is needed. Once the higher precision content is obtained, the content can either be displayed on a higher bit depth display such that the steps between two consecutive luminance levels are too small to be perceptible, or a half-toning technique (e.g. super dithering) can be utilized to quantize the higher precision content to the display bit depth and remove the perceptual artifacts due to the spatial averaging characteristics of human visual system.
Either way, obtaining a higher precision content for the smoothly changing area is an essential step in removing the abovementioned perceptional artifacts. The conventional systems do not address such problems.